This counter-current dual-flow air/air exchanger (1) includes a first network of channels oriented along a longitudinal axis (X-X′) of the exchanger (1), suitable for the circulation of a first airflow (F1) in a first direction, and a second network of channels oriented along the longitudinal axis (X-X′) of the exchanger (1), suitable for the circulation of a second airflow (F2) in the direction opposite the first airflow (F1). The exchanger (1) includes members (10, 12, 14) for reversing the flow direction of the second airflow (F2) in the second network of channels, such that the first and second airflows (F1, F2) circulate co-currently, suitable for protecting the exchanger (1) from ice.